1. Field of the Invention
The present invention relates to an information recording apparatus for writing information (data) onto a DVD-RAM (DVD-Random Access Memory), which is capable of reading out information and also writing information.
The present invention also relates to an information recording medium on which information is written by the information recording apparatus.
The present invention further relates to an information reproducing apparatus for reading the information recorded on the information recording medium.
2. Description of the Related Art
A DVD (Digital Video or Versatile Disk) is a recording medium having the about seven times capacity as compared with that of a conventional recording medium such as a CD (Compact disk), an LD (Laser disk) or the like. Recently, the research and development about a DVD are done, especially, the research and development about a standard of a DVD-ROM (DVD-Read Only Memory), which is capable of only reading out the information recorded thereon in advance, are actively done.
Here, as one example of modulation and demodulation methods with respect to the DVD-ROM, so-called 8/16 modulation-demodulation method is proposed. The 8/16 modulation-demodulation method is briefly explained below.
The 8/16 modulation is a method to modulate digital record data, which is constructed by the unit of 8 bits, to code data, which is constructed by the unit of 16 bits, corresponding to each other. The code data is actually recorded onto the DVD-RON. In the 8/16 modulation, four modulation tables are used. In each of the modulation tables, each of the code data constructed of 16 bits corresponding to respective one of the record data constructed of 8 bits are described in advance. Namely, in the 8/16 modulation, one modulation table is selected from four modulation tables, and the record data is modulated to the code data by using the selected modulation table. At this time, the selection of the modulation table is done on the basis of discriminating information called "state information". Namely, the state information is determined in advance in view of so-called zero-run-length, i.e., the number of "0" bits which are arrayed at the end-part in the code data which is obtained to modulate one record data by using the 8/16 modulation. For example, when the n.sup.th record data is modulated, the state information, which is used for selecting the modulation table when the (n+1).sup.th record data (the next record data of the n.sup.th record data) is modulated, is obtained. Therefore, in case that the (n+1).sup.th record data is modulated, the modulation table is selected on the basis of this state information. Then, the (n+1).sup.th record data is modulated to the code data by using the selected modulation table.
On the other hand, the 8/16 demodulation is the method to demodulate the code data recorded on the DVD-ROM to the record data. In the 8/16 demodulation, for example, the m.sup.th code data is demodulated on the basis of the (m+1).sup.th code data (the next code data of the m.sup.th code data) by using the demodulation tables. In each of the demodulation tables, each of the record data corresponding to respective one of the code data are described in advance.
However, if the 8/16 modulation-demodulation method used for the DVD-ROM would be adapted for the DVD-RAM capable of reading out information and also writing information, a problem is posed as followings. Namely, in the DVD-RAM, information is not always continuously recorded (written) thereon in time sequence. More particularly, when information is recorded on the DVD-RAM, the information is recorded thereon by the unit of the data-sector constructed by a predetermined quantity (size) of byte-data in order to carry out the error correcting at the time of reproduction. Therefore, in case that the first information constructed of several data-sectors is recorded on the DVD-RAM at first, and next, the second information, which is unrelated to the first information, is recorded thereon, it may happen a case that the recorded data-sectors adjacent to each other are not in series between the first information and the second information. Namely, it may happen a case that the continuity of the data-sector between the first information and the second information is lost or destroyed.
In this case, there is no next code data, which follows the last code data placed at the end-part in the last data-sector placed at the end-portion in the first information, because the recording for the first information is completed when the last code data is recorded on the DVD-RAM. Therefore, if the 8/16 demodulation would be carried out with respect to the last code data, it cannot be done because the next code data, which follows the last code data, does not exist.